Reserved instances allow for deep cost savings, and have various models to give you a balance between flexibility and cost savings. Here are a few pointers to get you going down the right path:
- Reserved instances have no distinguishing technical features compared to regular on-demand instances.
- Reserved instances are not a specific EC2 resource; rather, they are a billing construct that gives you a discount for continuous usage that matches the subscription.
- Put simply, purchasing a reserved instance entitles you to a discounted hourly rate on an on-demand instance that matches the properties of the reserved instance.
- The discounted hourly rate will be of varying size, depending on how much you pay up front. As a general rule, the more you pay up front, the higher the discount.
When you purchase a reserved instance, you're required to specify the following properties:
- Platform: Linux/Windows
- Scope: Region or Availability Zone
- Instance Type: For example, m5.large
- Tenancy: Shared or dedicated
- Offering Class: Standard or convertible
- Term: 1-12 months or 1-3 years
- Payment Option: No upfront, partial upfront, all upfront
We'll explore the ins and outs a little later in this section. For now, let's dive in and see how to make a purchase.